The present invention relates to apparatus for inspecting bore holes, and more particularly, to a video camera device adapted for inspecting a bore hole with improved forward and side view illumination.
There are many instances where holes are bored into the earth, such as water, oil and natural gas wells. It is often desirable to insert a video camera into a bore hole. This allows a geologist to inspect stratification, fracturing and layering of various geological formations through which the bore hole penetrates. In addition, a bore hole is often lined with a casing or pipe and it sometimes becomes necessary to inspect the integrity of this pipe for rust, cracks, rupturing, uncoupling and other defects. It is therefore desirable to be able to inspect a bore hole lined with casing or pipe with a video camera in order to ascertain the existence, nature and location of such bore hole defects.
Rugged video camera apparatus has been developed and used commercially for inspecting bore holes. Typically a cylindrical metal outer housing has separate forward looking and side looking video cameras mounted therein, the latter being rotatable. Gyroscopes, flux gate North direction seekers and inclinometers have been mounted in the cylindrical housing to provide an indication of the location and orientation of prior art bore hole cameras. Lights are usually connected to the forward end of the housing for illuminating the region of the bore hole ahead of the forward looking video camera and within the side of the cylindrical housing for illuminating the region of the sidewall of the bore hole adjacent the side looking video camera. Power, control signals and video image signals are transmitted between the bore hole camera and surface monitoring components via electrical conductors incorporated into the insertion and withdrawal cable coupled to the rear end of the cylindrical housing.
A bore hole is often filled with a light scattering medium, such as water. In order to optimize the resolution of the video image it is important to reduce the common illuminated volume between the video camera and the scene being viewed. Prior bore hole cameras have used forward shining incandescent lights such as that disclosed in U.S. Pat. No. 4,855,820 of Barbour. U.S. Pat. No. 5,652,617 of Barbour discloses a bore hole camera with a light source connected to its forward end for a forward looking video camera and a separate side facing light source for a separate side looking video camera. Since the side facing light source and the side looking camera must be axially spaced along the cylindrical outer housing, angled parabolic reflectors and forty-five degree angled mirrors adjacent the camera lens have been used in an attempt to project the maximum amount of light in the field of view of the side looking video camera and reduce the common illuminated volume. Incandescent light bulbs frequently fail, and much time is wasted in extracting the bore hole camera from the bore hole, replacing the bulb and reinserting the bore hole camera back to the desired location in the bore hole, which can be hundreds, or even thousands of feet from the surface. In addition, incandescent light bulbs often do not provide adequate illumination. If multiple bulbs were used, too much power would be consumed and/or excessive heat would be generated.
It is therefore the primary object of the present invention to provide a video camera device adapted for inspecting a bore hole with improved forward and side view illumination.
In accordance with the present invention, a bore hole camera has a housing configured for insertion into a bore hole and having a longitudinal axis. A first video camera is mounted in a forward end of the housing for generating video signals representing an image of a forward field of view extending in a forward direction from the housing. A forward illumination device is mounted in a forward end of the housing for illuminating the forward field of view. A second video camera is mounted in the housing for generating video signals representing an image of a side field of view extending in a side direction from the housing. Mechanisms are provided for rotating the second video camera around the longitudinal axis of the housing to align the side field of view of the second video camera with a predetermined circumferential region of a side wall of the bore hole. According to one aspect of our invention, a side illumination device is mounted in the housing adjacent the second video camera and includes a light bending component for maximizing the amount of illumination that strikes the predetermined circumferential region. According to another aspect of our invention the forward illumination device comprises an LED light ring set back from a forward end of the housing to minimize back scatter. According to another aspect of our invention the second video camera is mounted in a tube rotatable inside the housing about a common longitudinal axis. According to yet another aspect of our invention, the side illumination device comprises a cylindrical array of LEDs. Angular segments of the cylindrical array of LEDs are energized to illuminate the field of view of the second video camera and it rotates to thereby conserve power and reduce the amount of heat otherwise generated if all of the LEDs in the cylindrical array were simultaneously illuminated.